There is no doubt that you are damaging you cervix or uterus. Although some people like it rough, for the women with a tilted uterus, this will be the cause of her requireing a hysterectomy and not ever being able to have a baby ever again.
So turn off the "Don't stop get it, get it" and put on the "Let's take it slow." From my understanding, however, you can use this position but you'll have to convert the position to a knee-chest position by bending your arms slightly to give you even more of an angle.
The same is so with Side Lying or spooning. Nothing is promised to us, however, so if all else fails, you may want to discuss with your doctor about techniques you can do to repositioned the uterus or a minor surgical correction.
Hope this answers your question!
REFERENCE(S)
1. Kim Elise Goldman, 2006.
Baby Making Sex
2. American Pregnancy Association, 2003.
Tipped uterus : American Pregnancy Association
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